1. Field of the Invention
The present invention relates to a barrier device, a lens barrel, and an imaging apparatus including the same.
2. Description of the Related Art
There has been proposed a lens barrel including a barrier device (barrier mechanism) provided in front of a photographic lens. The barrier device shields or opens the photographic lens when an imaging apparatus is shifted to a photographing state or a collapsed (retracted) state. For example, there has been proposed a barrier mechanism that includes a barrier member having two pairs of blade members (one pair is large and the other is small) attached to the front of the photographic lens such that the blades can be opened and closed, and a barrier driving unit that opens and closes the barrier member.
Japanese Patent Laid-Open No. 2010-39129 discloses a barrier device for a camera including first and second blade members, first and second engaging portions provided on a driving member, and first and second biasing members.
However, in the barrier device disclosed in Japanese Patent Laid-Open No. 2010-39129, closing springs each corresponding to a main barrier blade and a sub barrier blade are required, and this increases the number of components. In addition, this barrier device requires setting of the balance for the springs, which makes the structure complex. Further, in this barrier device, unnecessary friction is caused between the main barrier blade and the sub barrier blade when the barrier is opened and closed. Furthermore, in this barrier device, the wider angle the lens has, the larger the opening diameter of the barrier becomes. This decreases the space for the blade members and the opening springs therefor, and makes it difficult to secure enough fitting length for the rotary shaft of the blade members, resulting in easy detachment of the blade members during assembly.